Positive pressure coating device

ABSTRACT

Positive pressure devices for coating the internal surfaces of open-ended, hollow, elongated structures with uniform, adherent, fluid coatings comprise (i) a pressurizable container for the fluid, having a structure-receiving opening in the top, (ii) removable means for holding the structures to be coated vertically in the opening of the container and for providing a pressure tight seal at the opening, and (iii) means for pressurizing the surface of the fluid and for interrupting and releasing the pressure when the fluid rises to a pre-determined height in the structures to be coated.

[ 5] Nov. 26, 1974 2/1955 118/408 X 11/1968 West 118/5 ABSTRACT 7 Claims, 4 Drawing Figures Primary Examiner-John P. McIntosh Attorney, Agent, or Firm-Thomas .1. Bird, Jr., Esq.; George B. Finnegan, Jr.; Rocco S. Barrese Positive pressure devices for coating the internal surfaces of open-ended, hollow, elongated structures with uniform, adherent, fluid coatings comprise (i) a pressurizable container for the fluid, having a structurereceiving opening in the top, (ii) removable means for holding the structures to be coated vertically in the opening of the container and for providing a pressure tight seal at the opening, and (iii) means for pressurizing the surface of the fluid and for interrupting and releasing the pressure when the fluid rises to a pre- 118/5, 118/7, 118/50, 118/408 B05c 7/04 118/5, 7, 408, 50, 421; 134/152, 56 R, 166 R determined height in the structures to be coated.

8 X X m m 8 MIN 00 8 1 1 1 1 Laidig et United States Patent Ruzzo POSITIVE PRESSURE COATING DEVICE [75] Inventor: Joseph G. Ruzzo, Schenectady, NY

[73] Assignee: General Electric Company,

Milwaukee, Wis.

May 24, 1972 [22] Filed:

[21] Appl. No.: 256,466

[51] Int. [58] Field of 2,303,290 1l/l942 Michael...,...................... 2,349,444 5/1944 McGowan.....

2,392,229 l/l946 Cohen.........,.

AC LIME TANK 54 5c rk omc CONTROLLER SHEET 18F 3 70 ATMOSPHERE roams VAL v UID LEVEL SOURCE SENSOR PATENTE HSVZ 8 I974 mm u mm M am 1 \l M E M ELECTRONIC CONTROLLER A C LINE sum 30F a PATENTEL 35V 2 5 I974 FIG; 3

1 POSITIVE PRESSURE COATING DEVICE BACKGROUND OF THE INVENTION There are many filling devices available which accomplish their action by applying the forces of positive pressure, negative pressure (vacuum) or gravity either singly or in combination. Such devices are used to fill hollow containers with diverse products such as soft drinks, tooth paste, pills and cosmetics. However, such devices are not generally recognized to be useful for coating the inside of hollow structures with layers of fluids.

A number of open-ended, hollow, elongated structures, many of them tubular, but including also those which are rectangular, etc., are coated with liquids, such as molten agar or other adherent fluids and used as bacteriological or serological testing devices.

One especially useful device of this type is a culturing pipette, which in one commercial embodiment comprises a relatively thin tube, usually of thermoplastic material, about to 12 inches long and about oneeighth inch in outside diameter. The inside of the tube is coated with a layer of solidified nutrient agar. In use, the lower end of the culturing pipette is dipped into a fluid, such as urine, suspected of containing bacteria, and the fluid is sucked up into contact with the layer of nutrient agar. The fluid is then drained out and the treated tube is ready for incubation. Any bacteria will show their presence in the form of discrete colonies in the agar coating on the internal surface after several hours of incubation.

The wide demand for such tubes requires a means to mass produce the internal coating and the present invention provides a device which simultaneously coats the internal surfaces oflarge numbers of hollow elongated structures.

It is a primary object of this invention to provide a means to coat the internal surfaces of hollow structures.

It is a further object to coat the internal surfaces of such structures in a device which permits dipping the open ended tips of the structures into a reservoir of the coating fluid, the application of positive pressure to that reservoir so that a column of fluid is forced up the hollow structures, and means to drain the fluid column from the hollow structures so that a uniform, residual coating is left behind on the internal surface of the structures.

Another object is to provide a device which is capable of initiating this sequence of events semiautomatically, as with a push-button.

Another object of this invention, once the filling sequence has been started, is to terminate the filling automatically and to initiate drainage automatically once the fluid column reaches a predetermined fill height within the hollow structures.

Still another object of this invention is to provide a means for controlling the temperature of the fluidreservoir in order that molten fluids, such as hot, liquid agar, can be used as coating materials.

Another object of this invention is to provide a de vice capable of filling, draining and coating a multitude of open-ended hollow bodies simultaneously.

A further object of this invention is to provide a device which can be quickly loaded with a plurality of open-ended hollow structures prior to the coating sequence and just as quickly unloaded after completion of the sequence.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a pictorial diagram showing a production scheme useful to coat the internal surfaces of bacterial culturing pipettes with agar using a positive pressure device according to this invention.

FIG. 2 is a perspective view of one embodiment of a positive pressure coating device according to this invention, showing also a pressurized chamber holding a multitude of pipettes vertically in the coating device;

FIG. 3 is a perspective view of the pressurized holder shown in FIG. 2 and shows a multitude of pipettes gripped therein under pressure; and

FIG. 4 is a schematic, pictorial diagram of the preferred means to control filling in a positive pressure coating device of this invention and to terminate the operation at a pre-determined height in the hollow structure.

DESCRIPTION OF THE INVENTION In its broadest aspects, the present invention contemplates a positive pressure device for coating the internal surfaces of open-ended, hollow, elongated structures with uniform, adherent, fluid coatings, said device comprising i. a pressurizable container for said fluid, having an open-ended, hollow, elongated structure-receiving opening in the top thereof;

ii. removable means for holding the open-ended, hollow, elongated structures vertically in said container and for providing a pressure tight seal at the structurereceiving opening of said container; and

iii. means for pressurizing the surface of said fluid and for interrupting and releasing said pressure when said fluid rises to a pre-determined height in-a vertical, open-ended hollow, elongated structure dipping into said fluid or into a second fluid of about the same specific gravity and viscosity.

Preferred embodiments will include means to heat and control the temperature of the fluid; adaptations to accommodate bacteriological or serological testing devices, such as culturing pipettes; and means to hold such pipettes in the positive pressure coating container.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a production unit is illustrated, comprising the following basic solutions: fluid (e.g.,' agar) container 2, holding fixture 4 for a plurality or bundle of source, e.g., a gas cylinder, is confluent with container 2 through pressure line 8. There is a large lumen or opening in the top of container 2 to accommodate holding fixture 4.

Holding fixture 4 is a tube holding device which mates with lumen or opening 10 of fluid container 2 so that the tubes or pipettes are held in position with their tips dipping into fluid 6. Container 2 and holding fixture 4 are easily assembled and disassembled from one another and together they define a closed, pressurable system.

The optional temperature controlling system may consist of a thermometer, a sensor attached to the thermometer, an electronic controller, and heating element 14. The temperature of fluid 6 in container 2 is measured with the thermometer/sensor l2, and heating element [4, e.g., an AC-powered mantle, maintains the fluid at a predetermined temperature via feedback from the sensor to the electronic controller.

The liquid level sensing system in .this embodiment comprises control tube (e.g., pipette) 16, a liquid level sensor, and an electronic controller. Control tube 16 dips into the reservoir of fluid 6 or into a container of control fluid similar in specific gravity and viscosity to the coating fluid. The liquid level sensor is preferably of the type which can be attached to control tube 16 and detects liquid level height within the tube. The sensor feeds back to the electric controller which, in turn, is connected to an optional activator, e.g., a push button activating box.

The pressurizing system comprises a pressure source, e.g., a gas cylinder, a three-way solenoid valve 40, and an optional, safety toggle valve openable at the atmosphere. The pressure source is confluent with container 2 via the solenoid valve, the action of which controls the pressurizing and depressurizing of container 2.

An activating means can consist of a simple alternating current push button circuit in which the input interfaces with the electronic controller of the liquid level sensing systemand the output with the coil of solenoid valve 40. As will be described more fully hereinafter, the coating sequence is initiated by pushing the button mounted on activator 38 and is terminated automatically by the liquid level sensing system.

A more detailed understanding of the invention can be gained by reference to FIGS. 2 and 3 which illustrate a device capable of producing in excess of 45,000 agarcoated pipettes in an 8 hour working day. The methods, materials and dimensions described in connection with this device are not intended to limit the scope of this invention in any way.

FIG. 2 shows the coating device with a tube holding fixture, containing a multitude oftubes ready for filling. Fluid container 2 is a 6% inch high clear acrylic (or polycarbonate or the like) cylinder with an 8% inch inside diameter. A inch thick circular piece of acrylic forms removable top 17 which mates with the cylinder via a circular groove fitted with a rubber gasket.

For convenience, fluid container 2 is secured to fourlegged stationary base 18. Top 17 is easily dissembled from the container proper by removal of wing nuts 20, which hold the unit fast to base 18. Top 17 has a rectangular structure receiving opening or lumen 10, measuring 7% inches X 3% inches and opening 10 is lined with a rubber gasket which receives tube holding fixture 4.

In FIG. 3 is shown a detailed view of one type of preferred tube holding fixture. This is a unique pressurizable chamber 4 which grasps and holds bundles of pipettes 22 pneumatically. The acrylic (or similar material) fixture is 7% inches X 3% inches X 1-5/16 inches thick and fits into opening 10 of fluid container 2. The interior of chamber 4 is hollow and it has 1** inch diameter holes drilled into it such that the holes align top and bottom. The device can have any number of pairs of holes, and the version shown in FIG. 3 has three. The chamber includes means to seal the holes to interconnecting tubular diaphragms. In the embodiment shown, tubes cut from l i inch OD X 1% inch ID acrylic and integral flanges 24 are fitted to the tops and bottoms of each hole and are interconnected with thin, tubular, flexible, fluid impermeable diaphragms 26. A seal at the top and bottom of each hole (e.g., an O-ring seal) keeps the tubes and rubber diaphragms in place and also seals off the hollow interior of chamber 4, this forming a closed system. A gas inlet port, such as tubless tire valve 28 provides the only opening into the interior of the chamber. When in use, pipettes 22 are dropped through the holes and the chamber is pressurized with a source of gas, such as an air inflating chuck. One to three pounds of pressure are more than enough to cause the rubber diaphragms to expand around the bundles of pipettes 22 so that they are flrmly held.

The three-hold pressurizable chamber shown in FIG. 3 will hold 25 3/ l 6 inch OD pipettes per hole for a total of pipettes. Of course, one, two, and four-hole chamber/holders can also be provided.

It will be obvious that coating bundles oftubes by the process described herein requires that the tubes have tapered tips, as in the case of pipettes. If the tips were not tapered, the longitudinal, interstitial spaces in a bundled arrangement of tubes will also fill with agar when the fluid container is pressurized. However, the simultaneous coating of a multitude of tubes with nontapered tips may be accomplished by using a tube holding fixture which holds many tubes such that none of the tubes contact one another so as to form interstitial spaces.

Again referring to FIG. 2, the optional temperature controlling system can be seen to consist of heating element 14 (in this case a heating tape) surrounding fluid container 2, thermometer 30 which protrudes through the left side of top 17 and sensor 32 attached to the thermometer with metal clips. The sensor is wired to an electronic controller (not shown). The electronic controller, in turn, controls the flow of current from a power supply (not shown) to heating element 14.

With thermometer 30 dipping into fluid 6 in container 2, the electronic controller is activated and deactivated at predetermined temperatures via capacitance changes across the clips of sensor 32 caused by changes in the height of the mercury column within thermometer 30. Temperature control of coating fluid 6 is thus maintained by the proper location of the sensor clips and by the alternate on and off heating of tape 14 as dictated by the level of mercury in thermometer 30. Uniformity of temperature through the fluid reservoir is facilitated if the fluid is stirred, e.g., with a magnetic stirring bar and magnetic stirrer 34 shown located beneath stationary base 18.

Referring again to FIG. 2, a vertical, open-ended hollow, elongated structure, e.g., control pipette 16, of the liquid level sensing system can be seen protruding through the right rear of top 17 and dipping into fluid 6 (e.g., molten agar) in container 2. Attached to control pipette 16 via metallic clips is liquid level sensor 36. Sensor 36 is a capacitance sensor similar to temperature sensor 32 and it is attached to its own electronic controller (not shown).

Because molten fluids such as agar leave a residual coating on the control tubes or pipette 16, the capacitance of the tube can tend to change eratically from one filling sequence to the next. Therefore, it is often desirable to use a beaker of a noncoating control fluid to operate the liquid level sensing system. A solution of water and glycerin adjusted to approximately the viscosity and specific gravity (density) of the coating fluid works well for this purpose.

Referring again to FIG. 2, push button activating box 38 carrying push button 39 and fuze 41 can be seen mounted to the right front of stationary base 18. Threeway solenoid valve 40 is mounted at the right rear of base 18. Toggle valve 42 mounted between activating box 38 and three-way solenoid 40 is simply a safety valve which can be flipped open to atmosphere to vent excess line pressure.

The coating action takes place as follows: the liquid level sensing system, the push button activating box, and the three-way solenoid valve act in unison to alternately pressurize and depressurize the fluid container. The pressure source (not shown) may consist of a tank of dry nitrogen metered with a two stage regulator. The means by which the coating action is achieved can be understood by reference to FIG. 4, which shows the interrelationship between these systems when the coating device is on standby.

The standby position is that position in which no fluid columnis in the control pipette l6, normally open switch 44 is open, normally open first relay 46 and second relay 48 aredeenergized. and fluid container 2 is open to atmosphere through ports 50-and 52 of threeway solenoid valve 40. In the standby positionthe electronic controller supplies power to push button activating box 38. However, since push button switch 44 and first relay 46 contacts are both normally open, no current flows to the coilsin first and second relays 46 and 48.

. With pipettes held in place in a holding fixture such that their tips are dipping into the agar, the coating sequence is initiated by pushing switch 44. This action causes second relay 48 to immediately energize such that fluid container 2 is pressurized through ports 50 and 54 of valve 40. Concurrently, first relay 46 is energized so that its normally open contacts close, thus keeping the pressurizing circuit locked in even after switch 44 is released.

The fluid in control pipette l6 rises simultaneously with the agar in the pipettes which are being coated.

When the agar rises to the desired height, i.e., when the column in control pipette l6 rises to the present fill height, the capacitance change across the metal clips of sensor 36 causes the electronic controller to temporarily interrupt power to activating box 38. This causes relays 46 and 48 to de-energize and the container is once again permitted to vent to the atmosphere. The contacts in relay 46 return to their normally open position. The pipettes subsequently drain and are left with a uniform agar coat. Total time to fill and drain is less than five seconds.

It should be noted that power to activating box 38 is immediately restored once the fluid in control pipette l6 begins to drain since the fluid column drops below the control height. However, the pressurizing circuit has been locked out" with the opening of the contacts in first relay 46. Thus, the sequence cannot be reinitiated until a fresh batch of pipettes is placed into container 2 and switch 44 is again closed.

From the foregoing description and examples it is obvious that a useful device has been discovered for coating the interior surfaces of a multiplicity of openended, hollow structures. Although the device has been shown to be useful in the manufacture of bacteriological culture pipettes by coating the interior thereof with uniform layers of molten agar, it is also intended that the device be adapted to coat other types of structures, particularly tubular structures, with other types of fluids when the need arises. Obvious modifications will suggest themselves to those skilled in the art.

The invention is not to be limited by the above'description but is to be defined only by the appended claims.

I claim:

1. A positive pressure device for coating the internal surfaces of open-ended, hollow, elongated structures with uniform, adherent, fluid coatings, said device comprising i. a pressurizable container for said fluid, having an open-ended, hollow, elongated structure-receiving opening in the top thereof;

ii. removable holding fixture means attached to the top of said container in pressure tight relationship for holding at least one bundle of said open-ended hollow, elongated structures vertically extending into said container, said fixture means being providedwith means for gripping said bundle and said fixture means being adapted toprovide that the open ends of said elongated structures can be dipped in said fluid in said container;

iii. means for pressurizing the surface of 'said fluid when said open-ended hollow, elongated structures are clipped in said fluid;

- iv. a vertical, open-ended hollow, elongated control structure dipping into said fluid;and

v. means associated with said control structure for interrupting and releasing said pressure responsive to said fluid rising to a predetermined height in said control structure.

2. A device as defined in claim 1 including vi. means for heating and controlling the temperature of said fluid.

3. A device as defined in claim 2 wherein the means for heating and controlling the temperature of said fluid comprises, in combination, a power supply, an electrical element for heating the fluid, and a temperature level sensor immersed in said fluid to close the electrical circuit when the temperature in the fluid falls below a pre-determined level and to open the electrical fircuit when the temperature exceeds a predetermined evel.

4. A device as defined in claim 1 wherein said openended, hollow, elongated structures are bacteriological or serological testing devices and said fluid is nutrient agar.

5. A device as defined in claim 4 wherein said bacteriological testing devices are culturing pipettes.

6. A device as defined in claim 1 wherein said removable holding fixture means for holding said elongated structures in said container is a pressurizable chamber, said chamber including gripping means comprising at least one thin tubular, flexible, fluid impermeable diaphragm sealed to the walls of at least one pair of apertures vertically aligned at the top and bottom of said chamber, said tubular diaphragm and apertures being sized to accommodate a bundle of culturing pipettes.

7. A device as defined in claim 1 wherein the means for pressurizing the surface of said fluid and for interrupting and releasing said pressure comprises an external source of gas pressure in openable communication with the container above the surface of said fluid, and said meansassociated with said control structure comprises a liquid level sensor at a pre-determined height determined level. 

1. A positive pressure device for coating the internal surfaces of open-ended, hollow, elongated structures with uniform, adherent, fluid coatings, said device comprising i. a pressurizable container for said fluid, having an openended, hollow, elongated structure-receiving opening in the top thereof; ii. removable holding fixture means attached to the top of said container in pressure tight relationship for holding at least one bundle of said open-ended hollow, elongated structures vertically extending into said container, said fixture means being provided with means for gripping said bundle and said fixture means being adapted to provide that the open ends of said elongated structures can be dipped in said fluid in said coNtainer; iii. means for pressurizing the surface of said fluid when said open-ended hollow, elongated structures are dipped in said fluid; iv. a vertical, open-ended hollow, elongated control structure dipping into said fluid; and v. means associated with said control structure for interrupting and releasing said pressure responsive to said fluid rising to a predetermined height in said control structure.
 2. A device as defined in claim 1 including vi. means for heating and controlling the temperature of said fluid.
 3. A device as defined in claim 2 wherein the means for heating and controlling the temperature of said fluid comprises, in combination, a power supply, an electrical element for heating the fluid, and a temperature level sensor immersed in said fluid to close the electrical circuit when the temperature in the fluid falls below a pre-determined level and to open the electrical circuit when the temperature exceeds a predetermined level.
 4. A device as defined in claim 1 wherein said open-ended, hollow, elongated structures are bacteriological or serological testing devices and said fluid is nutrient agar.
 5. A device as defined in claim 4 wherein said bacteriological testing devices are culturing pipettes.
 6. A device as defined in claim 1 wherein said removable holding fixture means for holding said elongated structures in said container is a pressurizable chamber, said chamber including gripping means comprising at least one thin tubular, flexible, fluid impermeable diaphragm sealed to the walls of at least one pair of apertures vertically aligned at the top and bottom of said chamber, said tubular diaphragm and apertures being sized to accommodate a bundle of culturing pipettes.
 7. A device as defined in claim 1 wherein the means for pressurizing the surface of said fluid and for interrupting and releasing said pressure comprises an external source of gas pressure in openable communication with the container above the surface of said fluid, and said means associated with said control structure comprises a liquid level sensor at a pre-determined height above the bottom opening of said control structure, and means actuatable by impulses from said sensor for venting pressure from said container when the level of liquid in said control structure rises to said pre-determined level. 